Energy-saving tips

Cover the pool

Evaporation is a major cause of heat loss from swimming pools. The water that evaporates carries heat away, leaving colder water behind. By covering the pool, you can avoid this heat loss.

Some pool covers for heated pools are good insulators and can reduce heating costs by up to 75%. Typical simple payback periods are around 2.5 years. Some have translucent bubbles and act as a greenhouse - they let solar heat in to heat the water, but don't let it out easily. These covers can increase the water temperature by several degrees.

Covers also help to prevent dirt getting into the pool, slow algal growth and avoid pool chemicals being degraded by the sun.

Insulate your pool underneath

If the ground surrounding your pool is colder than the water temperature, some heat will escape. You can prevent this by insulating the bottom and sides of the pool where possible.

Some commercially available pools, both small and large, include insulation.

Note: the amount of heat lost into the ground is normally much less than the amount lost into the air.

Other tips

While you need shady areas near a pool for UV protection, pools will not absorb solar heat if they are in shade.

When you build a concrete pool, consider having a 20-50cm wide strip painted black around the pool walls just under the water surface to provide passive heating.

Enclosing the pool

Building a greenhouse or conservatory over the pool will keep the wind and rain out, and will also increase the air temperature inside. The heated air will warm the water.

Even when you don't use the pool, the conservatory will be a pleasant place to relax.

The cheapest form of conservatory is probably the plastic sheet type used in garden centres and horticultural greenhouses.

Choose glazing or plastic that reduces exposure to ultraviolet rays - overexposure can cause skin cancer. It will also reduce UV damage to the plastic components of a swimming pool.

A heated swimming pool within a building can act as a large thermal mass helping to keep a moderate temperature all year round. But it will also add a lot of moisture to the air which can cause condensation.

Solar pool heaters

There are various solar pool heating systems available.

These systems cost little to run - the main cost is the electricity for the pump. Over the life of the system, the total cost will end up cheaper than systems that use gas or electricity. Solar heating is also better for the environment than gas or electrical heating.

However, water temperature is more difficult to control with solar heating systems.

Regular maintenance is necessary to ensure continued efficient operation.

Black plastic pipe systems

Black plastic pipes can get quite hot if left in the sun. A system of black plastic pipes can be fixed to a roof, pool fence, or frame where they can absorb the sun. Water pumped from the pool through the pipes heats up and is then transferred back into the pool.

To raise the pool temperature by 3-8°C, you'll need the plastic tubes to cover an area at least half as big as the pool itself.

Typical costs are from $3,500 to $7,000, installed for a family-sized pool.

Wind causes these systems to lose heat, so enclosing the pipes in glass or plastic with insulation beneath them increases efficiency.

There are several systems available that use this principle. These systems are always custom-designed for your pool as each situation is different.

Solar panels

Solar panels, similar to the ones used for domestic solar water heating, can also be used to heat swimming pools. But you'll need more panels than you would for a water heating system.

The area of the panels can be quite large, so finding a place to put them can be a challenge. A nearby, north-facing roof may be the best option.

You'll need a pump to circulate the water. Speak to the manufacturer of the system to ensure you get the correct flow rate for your pool.

This type of system is more expensive than the black plastic pipes, but can give useful heat for more of the year. Also, it will not lose as much heat in the wind.

Solar panels are more likely to be useful for school or public swimming pools where the extra cost is justified.

Installation and implementation

Solar pool water heating systems need to be designed by someone who understands how they work and what your specific requirements are.

The installation of a roof-mounted system must allow for considerable expansion and contraction of the pipes in the sun. If the pipes are fixed incorrectly, this can cause leaks in the roof.

Also, a roof-mounted system must be able to withstand any strong winds that may occur.

From ConsumerBuild

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Use the Homestar™ online tool to see how well your home performs and get advice on the steps to improving it, or book a certified assessment.

Make the most of free advice from an Eco Design Advisor, if your council offers it, or try the Home Energy Advice Centre for advice on heating options to suit your circumstances. Use Landcare Research’s carboNZero calculator to figure out your home’s carbon footprint.